Telephone-exchange system.



g H. CLAUSEN & C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED Npv. 9. I9|6.

i y -i w g Patented Apr. 23, 1918.

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inn snare earner canton HENRY 1P. CLAUSEN, 0F MOUNT VERNON, AND GHARLES L. GOODRUM, 0F BROOKLYN, NEW YORK, ASSIGNORS T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A OOBIPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

' Specification of Letters Patent.

Patentedjapr. 23, i918 Application filed November 9, 1916. Serial No. 130,372.

tively, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to such systems in which trunk circuits are employed for interconnecting subscribers lines terminating in difierent central ofiices.

The object of this invention is the provision of improved signaling means for such systems whereby the time required for establi'shing connections between subscribers may be reduced.

In accordance with this invention, there is provided at each end of a trunk circuit apparatus which'cooperates upon the con nection of a link circuit with one end thereof to select the character of ringing current to a called line,thereby determining which of a plurality of stations on a telephone line connected with the other end; of the trunk circuit is to be signaled. 2

This invention-a in one of its embodiments, is illustrated in the accompanying drawing, showing a trunk circuit C extending between two central oflioes, the apparatus to the left of the vertical dotted line being located at the first or originating central oi'licc and that to the right thereof being located at the second or terminating central oliice. A cord circuit A (a portion only of which is shown), located at the first central ofiice, may be employed in connecting a calling telephone line (not shown) with the outgoing end of the trunk circuit C. The incoming end or the trunk circuit C, terminating at. the. second central ofiice, may be connected "with the jack of a telephone line B, to which are connected four stations. I), E, F and G,

the apparatus of which is of the usual construction, the call bells of the different stations being tuned to respond to alternating currents of different frequencies. 7

Before proceeding with the operation of the system shown in the drawing,'a word of explanation regarding some of the apparatus employed may be in order.

Located 'at the first central ollice, and associated with the trunk circuit, are four jacks 5, 6, 7 and'8,'the, contacts' of which are connected with fixed terminals oi! an automatic switch 9. Associated with the four jacks are four relays 15, 16, 1.7 and 18,

'there being one individual to each jack, and

a relay 14' common to all four jacks.

' motor magnet 10, when actuated, serves to rotate the brushes 11, 12 and 13' ot' the automatic switch 9 over the fixed terminals thereof. The automatic switch 9 is of the step-by-step. type, the stepping pawl of which is controlled by the motor magnet 10,

, and the holding pawl by release magnet Theholding pawl is-normally in engagement with the ratchet wheel of the automatic switch 9 and is withdrawn therefrom when the release magnet is actuated to permit the switch to return to its normal position.

Located at the other end of the trunk circuit, there is an automatic switch 29 having four fixed terminals, tolwhich are connected four generators 35, 26, 27 and 2-8 for generating alternating currents of different frequencies. A movable contactil of the automatic switch 29 is controlled by a motor magnet 20, adapted to be actuated in synchronism with the motor magnet 10. The automatic switch 29 is also of the step-bystep type, the stepping pawl of which e advised that connection is desired with a subscriber whose line terminates at the second central oliicc, communicates the number of the wanted line to the operator at the second central. oilice over a call wire circuit (not shown) and receives a trunk assignment. Assuming that trunk circuit C has been assigned, and that subscriber G' on line B, whose call bell is tuned to respond to current from generator 28, is the subscriber auction is desired, the oper a crmtral liice inserts the plug ant f1. into jack 8, whereupon ml 18 onerate, the operation of enei slow release relay 30,

and latter connecting around to the test terminal of the automatic switch 9, asso- .iated. with jETaCl. The actuation of slow release relay 30 con'ipletes an operating circuit for motor magnet 10, but before the motor magnet operates, relay 40 operates, due to an impulse of current from battery, through winding of release magnet 32 (which is marginal and does not operate when in circuit with relay e0), leithand contact of relay 30, middle normal contact of motor magnet 10., left-hand winding of relay ll), right-hand normal contact of motor magnet 10, and right-hand contact of relay to ground. Relay 4-.0 operates,

lighting;- lan'ip 41 and causing the operation oil release magnet which is slow in releasing. The actuation of release magnet 42 throws the holding pawl into engage ment with the ratchet wheel of switch 29. The energization and operation of motor magnet 10 moves the brushes 11, 12 and 13 into contact with first or letthand set of contacts, and closes an off-normal contact 31. is not grounded, no circuit is completed for relay 33. The motor magnet 10, in operating, interrupts its own circuit at its lefthand contact. W hen the motor magnet 10 operated, its right-hand and middle normal contacts were opened, thereby releasing relay 40, whereupon motor magnet 20 slow release relay 43 operate over a circuit from battery through the windings of mo tor magnet 20 and slow release relay 43 in parallel, contact 44 (which is closed when automatic switch 29 is in normal position), contact of release magnet 42 and normal contact of relay 10 to ground. Release mag net 42 being slow in releasing, holds contact closed and the holding pawl in engagement with the ratchet wheel of switch 29 While the alternate contact of relay id is open during the stepping period.

The operation of motor magnet 20 ad vances movaole contact or brush 21 of automatic switch to the contact to "avl'iich generator 25 is c jar-c ted, and opens contact 4-4. and closes contact which is open when autou tch is in normal position. 'i" of relay 43 opens h H- I v r1ght-hanrl contact and closes its lei *hancl contact, which new substituted for contact 44c, opened by of i'notor net 2G. Relay 43, ei-g slow 1n role at-sing;

its contacts remain closed While the norr t0 1.3 open during the s o The closure cc act does ping period. not in; the! Since the test terminal ot the first set hand normal contact and the contact of trip relay Since motor magnet 10, in operating, opens its operating circuit, it releases, whereupon relay 40 again operates. Motor mag- 20 thereupon releases. Motor magnet 10 when fully released again completes its operating circuit, whereupon it operates to advance brushes 11, 12 and 13 to the second position. Upon the operation of motor magnet 10, relay 4O releases to complete the operating circuit of motor magnet 20, which thereupon operates to advance brush 21 of switch 29 to the second terminal to which generator. 26 is connected. Both motor magnets continue to operate the switches until the brushes of switch 9 aglyanoeto the fourth set or": terminals, when relay 33 operates to lock up motor magnet 10, the circuit being from battery, Winding of motor magnet 10 and relay 83, brush 13, test terminal of fourth Set associated with jack 8, contact of relay 18 to ground. When motor magnet 10 is locked up, motor magnet 20, due to the release of relay 40, advances the brush 21 to the fourth terminal to which is connectcd generator 28. Upon the connection of the brushes of switch 9 with the fourth set of terminals corresponding to the jack 8 to which a cord circuit A is connected, relay 40 is operated from battery in the cord circuit A, and remains operated as long as the plug of the cord circuit is in the jack. Since relay 40 is now locked up, release magnet is locked up, whoreup'bn relay 41-3 releases, conncctnlg alternating current with the jack of line B as soon as a trunk assignment is made. The operation of relay 48 opens the circuit of lamp 41 and locks up release magnet independent of the condition or the outgoing end of the trunk ci Upon the response of subscriber at iarion G. tripping; relay 47 operates, re-

; no; the short circuit of relay l6, which operates a circuit from battery, ,ough the winding oi relay 46, resistance 49. and contact to ground. Relay 46, in operating, opens its left-hand normal contact, thereby removing ringing current from the line. Supervisory relay 60 now operates over circuit from battery through Win oi supervisory relay 60, left land ate contact of relay 46, righthand contact of relay 43, ring contactsof the plug and jack out and back over line B, tip contacts of the jaclnand plug, and right-hand Contact of relay 48 to ground. Upon the actuation of supervisory relay 60, the right-hand winding of relay is connected in parallel with the left-hand winding thereof to cause the operation of the supervisory relay in cord. circuit A and extinguish the supervisory lamp (not shown).

Upon. the conclusion of the conversation,

subscriber G restores the receiver to the switchhook, releasing supervisory relay 60, whereupon the calling supervisory lamp in cord circuit A lights to furnish a disconnect signal. The operator at the first central oflice thereupon withdraws the plug from jack 8.- Relays l4 and 18 thereupon release, the release of the former causing the operationv of release magnet 32 over a circuit from battery through the winding of release magnet 32, contact 31 and normal con tact of relay 14 to ground. The operation of release magnet 32 withdraws the holding iawl from the ratchet. wheel of switch 9. The release of relay l8 permits the release or" relay 33 and motor magnet 10, whereupon switch 9 returns to normal position opening contact 31, whereupon release magnet 32 releases. Upon the release of motor magnet 10, relay 4:0 releases lighting the.

lamp all to furnish a disconnect signal to the operator. atthe second central oifice, who thereupon withdraws the plug from the jack releasing relay L8, thereby efiacing lamp ll and releasing the release magnet 42, whereupon switch 29 is restored to normal position, opening contact and closing contact eat.

What is claimed is:

1. A telephone exchange system comprising a trunk circuit extending from a first to a second central office, a pluralityof sources of signaling current at the second central office, a. plurality of terminals for the trunk .circuit at the first central oliioe corresponding to the sources of signaling current, a link circuit at the first central ofiice, and an elec- Lroanagnetic switching device in the trunk circuit operating upon the connection of the link circuit with any one of the terminals to. select the corresponding source of signaling current.

A telephone exchange system comprising a trunk circuit extending from a first to a second central ofiice, a plurality of sources of signaling current at the second central ofiice, a plurality of terminals for the trunk first central otfice corresponding to the sources of signaling current, a link circuit at the first central otfice, and an automatic step-by-step switch in eachend of the trunk circuit operating upon connection of the link circuit with one set of terminals to connect the trunk circuit therewith and to select the corresponding source of signaling current.

i. A telephone exchange system comprising a trunk circuit extending from a first to a second central ofice, a plurality of sources of signaling current at the second central oifice, a plurality of sets of terminals at the first central office corresponding to' the sources of signaling current, a link circuit at the first central ofice, an electromagnetic switching mechanism in each end of the trunk circuit operating upon connection of the link circuit with one set of terminals to connect the trunk circuit therewith and to select the corresponding source of signaling current.

5. A telephone exchange system comprising a trunk circuit extending from a first to a second switchboard, a plurality of sources of signaling current at the second switchboard, a plurality of terminals for the trunk circuit at the first central office corresponding to the sources of signaling current, a link circuit at the first central oflice, an electromagnetic switching mechanism in the trunk circuit operating upon the connection of'the link circuit with. any one of the terminals to connect the trunk circuit thereto and to select the corresponding source of signaling current.

In witness whereof we hereunto subscribe our names this 8th day of November, A. D. 1916.

' HENRY P. CLAUSEN.

CHARLES L. GOODEUM. 

